Pic. 155. Connection diagram of the carburetor solenoid valve control system: 1 - ignition coil; 2 - limit switch in the carburetor; 3 - control unit; 4 - solenoid valve; 5 - mounting block (fragment); 6 - ignition switch (fragment)
The control unit can turn off the valve only if the limit switch 2 of the carburetor is closed, i.e. if the accelerator pedal is not pressed. If you press the pedal, the valve will not turn off (or turn on if it was turned off).
Before checking the control unit, you must make sure that the wires are connected to it correctly (see fig. 155). The operation of the unit is checked with a voltmeter (with measurement limits 0-15 V) in the following order.
Disconnect the green wire from the carburetor limit switch and connect the tip of this wire to the body. Connect to the control unit. voltmeter 2 (pic. 156) using a special connector. They start the engine and, gradually increasing the speed, monitor the readings of the voltmeter: after starting the engine, it should show a voltage of at least 10 V, and at the moment the valve is turned off, an abrupt decrease in voltage to 0.5 V (no more).
Pic. 156. Scheme for checking the control unit of the carburetor solenoid valve: 1 - control unit; 2 - voltmeter with adapter; A - to the car wiring harness
The crankshaft speed is set within 2200-2300 rpm, the tip of the wire going to the carburetor limit switch is disconnected from the body, and then reconnected to the body. When the wire is disconnected from the body, the valve should turn on, and when connected to the body, it should turn off. After turning off the valve, gradually reduce the speed until the valve turns on. The voltmeter should show an abrupt increase in voltage to at least 10 V.
It is allowed to check the control unit without a voltmeter by the characteristic knock of the valve when turning it off and on.